In some computers, additional functionality may be added via swappable (i.e., hot-pluggable) plug-in devices known as “cards” or “modules.” When a card is plugged into an associated port or slot of a computer, the functionality of the card is accessible to the computer. If a user wishes, the card may be unplugged from one computer and plugged into another computer, thereby switching the functionality provided by the card from one computer to another.
In order for some cards to function, a computer that receives the card may need to periodically synchronize clock signals embedded in data packets with another clock signal. This periodic syncing may be performed by a reference clock. Unfortunately, permitting a reference clock to run continuously (whether or not a card is plugged in) results in increased power consumption and increased likelihood of electromagnetic interference (EMI). Further, altering an existing reference clock architecture (i.e., platform) is often costly and may cause compatibility problems.